At its meeting Wednesday, the air district board voted unanimously to accept the settlement agreement, called a consent decree. Officials with State Parks and the state Attorney General approved the deal March 20.

The agreement comes as managers at Oceano Dunes are beginning to implement $1 million in dust control measures at the park. These include installing 15 acres of wind fences in the park’s riding area and at least 5,000 hay bales in a buffer area between the park and populated areas.

The settlement is tentative because it still has to be approved by a Court of Appeal, said Ray Biering, attorney for the air district. Biering expects to submit the settlement to the Court of Appeal within the next couple of weeks, but no estimate of when the court will act on the settlement was available.

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Biering also said he plans to meet in a week or so with the off-highway riding group Friends of Oceano Dunes, which filed the original lawsuit, in an attempt to get them to sign off on the settlement. The settlement will only be valid if the Court of Appeal agrees to dismiss all the lawsuits against the air district.

Jim Suty, president of the Friends of Oceano Dunes group, was not available Wednesday to comment on the group’s intentions concerning the lawsuit.

Under the agreement, a requirement for State Parks to obtain a permit from the air district to carry out the dust rule, called Rule 1001, will be replaced with a dispute resolution process intended to allow the air district and parks officials to more cooperatively reduce dust emissions from the park.

The agreement also calls for appointing a mediator, called a special master, who can settle any dispute over implementing the dust rule between air district and parks officials.

The agreement represents the conclusion of six months of negotiations and mediation between State Parks, the air district and the state Air Resources Board, said Larry Allen, air pollution control officer.

“The consent decree represents a lot of hard work and shared willingness to develop a process that will work well for all parties,” he said. “The air district is ready to move forward with implementing Rule 1001 and work with State Parks to employ the measures needed to reduce particulate matter from the dunes and protect public health.”

If successful, the agreement will settle a dispute between county air officials and State Parks that began when the air district first adopted the dust rule in November 2011. The rule was adopted because the air district determined that Oceano Dunes was responsible for high particulate levels on the Nipomo Mesa that exceed state health standards some 65 days a year.

The $1 million in dust control measures is intended reduce emissions by 15 percent, Allen said.

Fifteen acres of wind fences have already been installed in the park. Between 5,000 and 6,000 hay bales over 30 acres will also be installed in non-riding areas of the park in April, said Brent Marshall, park superintendent.

“The state Air Resources Board wants a project on the ground as soon as possible,” he said. “This will definitely help our downwind neighbors but the cumulative effect has yet to be determined.”

The fences and bales work by slowing down wind velocity as it blows across open sand dunes enough to allow the tiny sand particles to drop out of the air.

Particulate monitoring devices will also be installed upwind and downwind of the wind fences and hay bales to measure their effectiveness.

The settlement agreement does not affect a separate lawsuit filed by the group Mesa Community Alliance against State Parks but not the air district over lack of progress in implementing dust control measures.

Arlene Versaw, spokeswoman for the Mesa group, said the group will only withdraw its lawsuit when air quality on the Mesa meets state health standards.

“The bottom line for us is that we still have a health issue,” she said.